Pros
Generally most people that you work with are down-to-earth and good to work with. The daily tasks change a lot, which keeps the day interesting. If you're into cars, this is a great position to work in, because you get to drive all kinds of vehicles and learn about true market values.
Cons
They say that they promote based off of merit, but this is not true. To get promoted from Buyer to Senior Buyer you have to jump through a million hoops, go through multiple panels, give presentations, have people analyze you who don't even work in your office critique you, all for a moderate at best raise. They're looking for someone who will talk the Carmax lingo and use all of their super corporate sayings, like "cascade" and "I'll circle back" amongst hundreds of others. You have to work nights and weekends, which gets old very fast. You are not compensated based off of your college degree or background. I know men and women who have their MA (hard times brought them here) and get paid a fraction of what they're worth. People who should not be managing and/or coaching people will get promoted simply because they fit the Carmax mold. They talk the talk and are incredibly bought in. They speak in Carmax language, which would sound ridiculous at any other major company. The feedback is endless. Any meeting you have, participate in, or have an opinion of, you will hear, "let me give you some feedback on that..." or "what's your feedback on that meeting?" The feedback...never...stops.